Internal-combustion engine



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March 27, w28.

A. c. slNcLAlR INTERNAL GOMBUSTION ENGLIBHI 2 Sheets-Sheet l Sept l5. 1922 INVENTOR. H Zf/Qm [f5/'nda /fg ATTORNEY mmh 7, 1928;

Filed sept. 15. 1922" 2 Sheets-Sheet 2 IN VEN TOR.

ATTORNEY.'

Patented Mar. 27, 719.28.4

ALFRED c. sINcLAIn, or NEW ORLEANS, LoUIsIANA.

IN'rEaNALcoMBUsTIoN ENGINE.

Application led Septemberl 15, 1922. Serial No.' 588,343.

It is the object of my invention to improve the operating characteristics, the eiciency, and the economy 'of atwo-stroke'cycle internal combustion engine. More specifically, it is my object to produce a practical two-stroke `cycle engine which operates with a substantially uniform consumption of air per cycle and with a substantially constant compression, but the power is controlled by varying the quantity of a separately supplied mixture; and in which this separately supplied mixture is forcibly injected int the combus- A tion chamber durmg the compression stroke,

at a point in such stroke which de ends on the throttling, and to produce t ereby a stratification of the fluid in the combustion chamber whereby there is always an isolated portion of mixture at the spark plug in condition for ignition.

The invention in this application is directed specilically to two-stroke cycle engines; but it involves a' generic invention which is not limited to two-stroke cycle e111-- gmes and is claimed more broadly in my co-A pending application, Serial No. 631,598, led April 12,A 1923. l

In carrying out my present invention, I provide in addition to the main cylinder and piston, to the combustion chamber of which air is supplied by crank-case compression at the end of the explosion stroke, a smaller supplemental cylinder and piston which drawsin by suction' explosivemixture from a carbureter and forces such mixture thus drawn in into the combustion chamber of the main cylinder, through a valve which prevents returnV flow,y the supplemental piston being substantiallywithout clearance in'its cylinder at one end of the'stroke and havlng an angular lead over the main piston in the cycle. The supplemental piston assists in the compression .ofthe airl in thecrank-case, to provide an additional volume for scavenging the main cylinder.

The accompanying invention: Fig. 1 is a vertical section through an engine embodying 'my invention, being taken in a plane perpendicular to the crankshaft to show one main cylinder with its supplemental charging cyllnder; andFig. 2 is a vertical section'taken longitudinally of .the crank-shaft substantially on the line 2-2 of Fig. 1 to show my invention embodied in a two-cylinder engine.

ISISv The engine illustrated is. a two-'cylinder engine, having two main cylinders 10, the

ldrawings illustrate l y 26 is drivingly connected piston 11 in each ofwhich is suitably connected'bya connecting rod 12 toa crank 13 on the crank-shaft 14. The number of cylinders 10, of course, is not limited to two, but may be anything desired. The pistons 11 and connecting rods 12 are omitted from Fig. 2, in order better to show the ports in the cylinder wall. These ports include exhaust ports y15 on one side of the longitudinal central plane of the cylinder and a1r-supply ports on the othersideof said central lon tudinal plane. The exhaust ports 15, which in Fig. 2 are shown only in dotted lines, have their upper edges higher than the upper edges of the air-supply ports 16, so that as the 'piston 11 descends it will uncover first thel exhaust ports 15 as it approaches the end of its down-stroke, but will not uncover the air-supply portsv 16 until it ets' slightly further down on such doWn-stroe. The ex- 'haust ports 15 may lead to any exhaust system. The air-supply ports I16 are supplied by thei compression of air in the crank-case ,fthe supply from the-crank-case to such aut-supply ports 16 being by passages 18 in the wall of the cylinder-,1w ich passa es 18 as shown communicate-.with the cra -case when the piston 11 .isat the lower end of its stroke l by way of ,openings 19 in the piston skirt. This arrangement of openings 19 in the plston skirt is merely amincident, how` ever, vto my invention, and is provided merely for economy of space because of the' necessities' of the supplemental or char 'ng cylinder and piston which will be descrlbed later. The head of the plsto'n 15 is provided `Conveniently, though not necessarily, each sup lemental cylin er and. piston 25- 26'is in t e saine lane transverse to the crank.

shaft 14 as 1s its associated main cylinder and piston 10--11, as that ermits a compactness and simplicity of esign which is desirable. This. particular arrangement is shown in Fig. 1. Each sup lemental piston y a connecting rod 27 to the crank-shaft 14, so that it will be reciprocated by the rotation of the crankshaft. As shown, the connection of the lower end of the connecting rod 27 is to va pin 28 carried by the head at the lower end of the connecting rod 12 at one side of said head, which causes the in 28 to travel in an approximately elliptical path 29 while the main ,crank 13 travels in its circular path 30. The precise shape of the path 29,

owever, is immaterial, and there is no great advantage in the elliptical shape, al-

though it does give the piston 26 a slightly longer stroke than\ that of the piston 11;

. The piston 26 hasjan angular lead in the (This lead of t cycle over the piston 11, by between 20 and in the engine illustrated; which lead is obtained in such illustrated engine by lhaving the 'cylinder 25 oblique to the cylinder 10 and converging downward therewith,

and by having the connecting rod 27 attached tothe lpin 28 in the manner shown. evpiston 26, however, is not necessarily obtainable in thisy Iparticular sok i 25. This mixture-inlet port 36 is preferably arranged to be uncovered only during the manner, though the construction illustrated produces the lead very satisfactorily. The

iston 26 when moved to the upper 'end of its stroke isv arran ed to leave substantially no space above it 1n the cylinder 25, to get substantiallythe complete expulsion pf. the

fluid from such cylinder.

The cylinder 25 is supplied `with a rich explosive mixture from a carbureter 35, the outlet of which leads to a mixture-inlet port 36 arranged in the side wall of the cylinder lower portion of the stroke of the supple- .i mental vpiston 26, to admit the supply at ficiently that time of arieh explosive mixture from the carbureter 35 into the cylinder 25, drawn in by the high vacuum then existing in suchl cylinder 25. This arrangement of the port cylinder 25 and past a spring-seated'checkf.

valve 38 into and through an ignition passage 39 and into the combustion space 40 at the top of the cylinder 10. This forcing in of the mixture from. the cylinder 25 into the combustion space 40 occurs during the up-stroke of the piston 11, beginning at a point in :such up-stroke'which is dependent upon the setting of the throttle 41 of the carbureter 3.5. A spark plug 42 is provided with its electrodes in the ignition passage 39,

for producing ignition at the proper point Aof the two pistons.

11 and 26 move downward, the supplemental in the cycle, which `point may beadvanced l 'a disk 50 on the end of the valve stem 48.

This spring 49 and its associated partsV arey enclosed, andthe valve-seat 'member 45 is clamped against the shoulder 46, by a hollow screw-plug 5l which is screwed in the `outer end of the hole 47. This construction of the check-valve 38, however, Vis merely an incidental feature of construction.

The air for compression in the crank-case 17 is supplied from .the atmosphere by way of an air-inlet passage 55, at the inner end,-

of which is an inwardly opening check-valve 56 for preventing the outflow of airwhich has been admitted. Preferably the air-inlet passage 55 has a supplemental opening 57 through the lowerIl part of the cylinder 25,- in position to be uncovered bythe skirt of the piston 26 during the upper part of the movement of such piston; this supplemental opening 57 assists in getting the crank-case 17 filled with air.

yThe operation is on The piston 26 in its reciprocation has a lea on the piston 11, as already explained, of between 20 and 25 in the engine shown. As the pistons 11 and 26 move upward, they the, two-stroke cycle.

.draw air into the crank-case 17 through the air linlet passage 55, past the check valve 56,

and (while the piston 26 is at'the top of the stroke) throughthe supplemental opening 57. The quantity of air thus drawn in is substantially the sum of the displacements When now the pistons piston 11 still maintaining its lead, the air which has been drawn into the crank-case 17 is compressed therein by the movement of' such pistons. When the piston 11 nears the bottom of its stroke, it uncoversthe-,ports 15 and 16 in succession. The uncovering of the ports 15 permits the outflow of the burned gases from the preceding explosion.l

Within the cylinder 10. The uncovering of the ports 16 occurs after the pressurewithin the cylinder 10 has been relieved bythe outflow of the burned gases, and when it occurs the air which has been compressed in' the crank-case by the downward movement of the pistons admitted from such crank-- case by the way of the openings 19 and passages 18 through such ports 16 into the cylinder 10. The air thus admitted is deflected upward by-the dellecting face 20, and pushes aheadof it the greater part of the remain? ing burned gases in the cylinder 10, which burned gases escape throu h the still open ports 16. More than a cy 'nder-full of air is supplied through the air-supply ports 16,

- because of the compression of a1r m the crank-case by both pistons 11 and 26, which materially helps in scavenging the cylinder 10. When the piston 11 starts upward, the cylinder 10 has within it substantially a cylinder-full of air, at substantially atmospheric pressure, with very little contamination from burnt gases from the preceding explosion, but with no ,/fuel mixed with this air. It is this air which is fundamentally compressed in the cylinder 10 by the up-strke of the piston 11, and it is compressed to a substantially constant volume and constant pressure.

The supplemental piston 26 at the bottom of its down-stroke has drawn in a rich mixture of air and fuel from the carbureter 35, by way of the mixture-inlet port 36. The amount of this mixture drawn in varies with the opening of the throttle 41. On the up-stroke of the supplemental piston' '26 which up-stroke is slightly in advance o that of the main piston 11, the mixture thus drawn into the cylinder 35 is compressed until its pressure is suilicient to open the valve 38; whereulp-n this compressed mixture from the cy der 25 is forced by the piston`26 through the opening 37 and past the check valve 38 into and through the ignition passage 39 and into the combustion chamber 40 of the cylinder 10. Durin this forcing-in of the mixture into the cy der 25, the air ing compressed by the upward movement of the piston 11. The point at which the valve 38 opens to allow the passage of the explosive mixture rom the cylinder 25 to the combustion chamber 40 varies with the amount of explosive mixture in such cylinder 25 at the beginning of" the up-stroke of the piston 26, and therefore is controlled by the setting of the throttle 41; the valve 38 opening earlier in. the cycle when the throttle 41 is wide open thanr when it is partly closed. Substantially the entire charge of the mixture in the supplemental cylinder 25 is `forced out of such cylinder because of the absence of any substantial clearance between the piston 26 and the head of the cylinder 25. Because this explosive lmixture actually forced into the combustion space 40, instead of being merely drawn in by suction, it is heated and not cooled as it enters such combustion space, which makes it much more ready for ignition. This mixture thus forced into the combustion space apparently stratifies to a greater or less extent with relation to the air already in the cylinder'lO, instead of mixingthoroughly therewith, although there is of course already in the cylinder 10 is be:

some mixing; and I believe the mixing is greater the earlier the valve 38 is opened.

In any case, I have found that for any throttle opening, and for any speed of the engine within wide limits, I obtain an ignitable charge in the ignition passage. 39; which charge is ignited when the spark occurs at the spark plug 42. "lhe combustion extends to, the explosive mixture in the combustion chamber 40, which is at a compression which varies comparatively slightly, and produces the explosion which forces the pistonl 11 downward on its explosion stroke.

I have described the operation of my engine in connection with a single main cylinder 10. The operation is substantially the same for each main cylinder 10, regardless of the number of cylinders; the pistons of .l

. the several cylinders being properly coninto sections corresponding to the number ofcylinders, vertical dividing walls 60 such as shown in Fig.2.

I claim as my invention:

1. lA two-stroke cycle engine, comprising a main cylinder and piston, a` supplemental cylinder and piston, means interconnectin said two pistons whereby the Supplemente' piston has an acute-angle lead over the main piston in theirvcycle of movement,l means for supplying explosive mixture to said supplemental cylinder, the ends of said two cylinders being interconnected by a passage of 'which'the end is never covered by the main piston in its movement, and a chamber in which air is compressed by the main` iston on its explosion stroke, said main cy inder being provided with exhaust ports and with air-inlet ports which are uncovered successively at the end of the explosion stroke of the main piston, said air-inlet ports com- I pressed by' the main vpiston on its explosion stroke," said main cylinder being provided with exhaust ports and with air-inlet ports which are uncovered at the end of the explosion strokeoil the main piston, said airnlet ports communicating with said cham- 3. A two-stroke cycle engine, comprising a main cylinder and piston, a supplemental cylinder and piston, means interconnecting said two pistons whereby the supplemental piston has a lead over the mainpiston in their cycle of movement, means for supplying explosive mixture to said supplemental cylinder, the ends of said two .cylinders being interconnected by a passage of which the end is never covered by the main piston in its movement, and a chamber in which air is compressed by the main piston on its exi plosion stroke, said main cylinder being proing interconnected by a passage of .which the end is never covered by the main piston in its movement, and a chamber in which air is compressed b strokes of both pistons, said main cylinder eing provided with exhaust ports and with air-inlet ports whichare uncoveredv successively at the end of the explosion stroke of the main piston, said air nlet ports communicating with said. cham- 5. A two-stroke cycle engine, comprisinoP a.v main cylinder and piston, a supplementa cylinder and piston smaller in displacement t an the main cylinder and piston, means interconnecting said two pistons whereby the supplemental iston has a lead over the main piston in tlieir cycle of movement, means for supplyin explosive mixture to said supplemental cy inder, the ends of said two cylinders being interconnected by a passage of which the end is never covered by the main piston in its movement and a chamber in which air is compressed by strokes of both pistons, said mam cylinder being provided with exhaust ports and with air-inlet ports which .are uncovered at the end of the explosion stroke of the main piston. said air-inlet ports communicating with said chamber,

6. A two-stroke cycle engine, comprising a main cylinder and piston, a supplemental cylinder and piston, meansinterconnecting said two pistons whereby the supplemental piston has a lead over the main piston in their cycle of movement, means for supplyin explosive mixture to said supplemental cy inder, the ends of said two cylinders being interconnected by a passage of 'which the end is never covered by the main piston in its movement, and a chamber in which air is lcompressed by strokes of both pistons, said main cylinder bein provided with exhaust ports and with alr-inlet ports which are uncovered at the end of the explosion stroke ot' the main piston, said air-inlet ports communicating with vsaid chamber.

7. A two-stroke cycle engine,-comprising ay main cylinder and piston, a supplemental cylinder and piston, means interconnecting said two pistons whereby the supplemental piston has a lead over the main piston in their cycle of' movement, means for supplying explosive mixture. to said supplemental cylinder, the ends of said two cylinders be-y ing interconnected by a passage of which the end is never covered by the main piston in its movement, a valve permitting flow through said passage only toward the main cylinder, and a chamber in which air is compressed by the main piston on its explosion stroke, said main cylinder being provided with exhaust ports and with air-inlet ports which are uncovered at the end of the explosion stroke of the main piston, said airnlot ports communicating with said chamer.

8. A two-stroke cycle engine, comprising a main cylinder and piston, a supplemental cylinder and piston, means interconnectin said two pistons whereby the supplementa piston has a lead over the main piston in their cycle of movement, means for supplying explosive mixture to said supplemental cylinder, the ends of said two cylinders being interconnected by a passage of which the end is never covered by the main piston in its movement, a valve permitting flow through said passage only toward the 4main cylinder, and a chamber in which air 4is compressed by strokes of both plstons,

said main cylinder being provided with exp haust ports and with air-1nlet`ports which are uncovered at the end of the explosion stroke of the main piston, said air-inlet ports communicating with said chamber.

9. A' two-stroke cycle engine, comprising a main cylinder and piston, a supplemental cylinder and piston, means interconnecting said two pistons whereby the supplemental piston has a lead over the main piston in their cycle .of movement, means for supplying explosivemixture to said supplemental cylinder, the ends of said two cylinders being interconnected by a passage of which the end is never covered by the main piston in its movement, a chamber in which air is compressedkby the main iston on its explosion stroke, said main. cy inder be- 4 ing provided with exhaust ports and with air-inlet ports which are uncovered att-he en'd of the explosion stroke of the main piston, said air-inlet ports communicating with said chamber, and a spark plug having its electrodes located in said passage.

10. A two-stroke cycle engine, comprising a. main cylinder and piston, a supplemental cylinder and piston, means interconnectmg said two pistons whereby the supplemental piston has a lead over the main piston in s their cycle of movement, means for supplyin explosive mixture to said supplemental cy inder, the ends of said two cylinders being interconnected by a passage of which the end is never covered by the main piston in its movement, a valve permitting flow through said passage only toward the main cylinder, a chamber in which air is compressed by the main iston on its explosion stroke, said main cy inder being provided with exhaust ports and with air-inlet ports which are uncovered at the end of the explosion stroke of the main piston, said airinlet ports communicating with said c ha'mber, and a spark plug having its electrodes located in said passage on 4the-main-cylinder side of said valve.

11. A two-stroke cycle internal combustion engine, comprising a main cylinder and piston, a crank-shaft connected to said main piston, a supplemental cylinder and piston, said supplemental piston also being driven l from said crank-shaft and being arranged to have a lead over the main piston in their lcycle of movement, a crank-case in which a1r is compressed by the movement of the main piston and. which is connected to said main cylinder by'passages which are opened when the main iston is at the lower part of its stroke, said main cylinder also having exhaust ports which are' controlled by the iston movement, a carbureter from whic explosive mixture is supplied to said supplemental cylinder by the suction ac` tion of said supplemental piston on its down stroke, and a valved passage between theA upper'ends of said two cylinders.

12. A two-stroke cycle internal combustion engine, comprising a main cylinder and piston,.a crank-shaft connected to said main piston, a supplemental cylinder and piston, said supplemental piston also being driven from said crank-shaft and being arranged to have a lead over the main piston in their cycle of movement, a crank-case in which air is compressed by the movement of both pistons and which is connected to said main cylinder by passages which are opened when the main piston 1s at the lower part of-its stroke, said main cylinderl also aving exhaust ports which are controlled bythe piston movement, a carbureter from which explosive mixture is supplied to said supplemental cylinder by the suction action of said su plemental piston on its downstroke, an a valved passage between the upper ends of said two cylinders.

13. A two-stroke cycle internal combustion engine, com rising a main cylinder and piston, a crank-s aft connected to said main piston, a supplemental cylinder and piston,l

which explosive mixture is supplied to said i supplemental cylinder by the suction action of said supplemental piston on its down stroke, a valved passage between the upper ends of said two cylinders, and a spark.

plug having electrodes in said passage which interconnects said two cylinders.

14. A two-stroke cycle internal combustion engine, comprising a main cylinder and piston, a crank-shaft connected to said main piston, a supplemental cylinder and piston, said supplemental piston also being driven from said crank-shaft and being arranged to have a lead over the mainv piston in their cycle of movement, a crank-case in whichl air is compressed by the movement of b'th pistons and which is connected to said main cylinder by passages which are opened when the main piston '1s at the lower part of its stroke, said main cylinder also havingexhaust ports which are controlled by the piston movement, a carbureter from which explosive mixture is supplied to said supplemental cylinder by the suction action of said supplemental piston on its down stroke, a valved passage between the upper ends of said two cylinders, and, a spark plug having electrodes in said passage which interconnects said two cylinders. v

15. A two-stroke cycle internal combustion engine, comprising a main cylinder and piston, a crank-shaft to which -the main piston is connected, a crank-case, said cylinder being provided with exhaust ports and with air-supply ports which are covered and uncovered by the piston movement, said airsupply ports being supplied with air by crank-case compression, and a supplemental piston and cylinder arranged to obtain explosive mixture by a sucking stroke of the supplemental piston, said supplemental cylinder being connected to the main cylinder by a valved supply assage of which the main cylinder end is a ways open vso far as movement of theV main pistonv is concerned, and means for driving said supplemeans for forming outside of said main cylinder a mixture of fuel and air and for forcing said mixture into said main cylinder during the compression, stroke of the main piston by a passage which remains open to the main cylinder to the end of said compresf sion stroke.

l 17. A two-stroke cycle internal combustion engine, comprising a main cylinder and piston, means associated therewith for supplying air to said main cylinder when-the main piston is at one end of its stroke, means for forming outside of said main cylinder a mixture of fuel and vair and for forcing said mixture into said main cylinder during the compression stroke of the main piston of which the main-cylinder end is always open sol far as movement of the main piston is concerned, and means for igniting said forced-in charge near its point of entrance into the main cylinder.

18. A two-stroke cycle internal combustion engine, comprising a main cylinderv and iston, means associated therewith for supp ying air to said main cylinder when the main piston is at one end of its stroke, means for forming outside ofsaid main cylinder a mixture of fuel and air and for forcing said mixture into said main cylinder during the compression stroke of the main piston, a conduit through which said previously formed-mixture is thus forced into the main cylinder and which is continuously open to said main cylinder, and ignition means in said conduit.

19. Al two-stroke cycle internal combustion engine, comprising a mainjcylinder and piston, means associated therewith for supplying air to said main cylinder when the main piston is at one end of its stroke, 'a sup\ plemental cylinder and piston, said'supplemental cylinder having lan inlet for receiving air and fuel and an outlet connected to the main cylinder, said outlet being located near the end of said supplemental cylinder, a'conduit by which said outlet from the supplemental cylinder is connected to the main cylinder, said conduit being permanently open to the combustion space of the main cylinder, and means for operating said supplemental piston with a lead over the main piston.

20. A two-stroke cycle internal combustion engine, comprising a main cylinder and piston, means `-associated therewith for supplying air to said main cylinder whenthe main pistonis at one end of its stroke, a supplemental cylinder and piston, ,said supplemental cylinder having. an inlet for receiving air and fuel and an outlet connected tothe main cylinder, means for operating said supplemental piston with a. lead over the mam piston, a conduit by which said outlet from the supplemental cylinder is connected to the main cylinder, said conduit beving permanently open to the combustion is never covere space .of said main cylinder, and ignition means in said conduit. 21. A two-stroke cycle internal combustion engine, comprising a main cylinder and.

piston, means associated therewith for supplying to said main cylinder when the main piston is at one end of its stroke a quantity of air 'greater thanv the displacement of said.

main piston, and means for forming outside of said main cylinder a mixture of fuel and air and for forcing said mixture into Said main cylinder during the compression stroke of the main piston, a conduit by which said outlet from the supplemental cylinder is connected to the main cylinder, said conduit being permanently open to the combustion n space of the main cylinder.

22. A two-stroke cycle engine, comprisin a main cylinder and piston, a supplementa cylinder and-piston, means interconnectin said two pistons whereby the rates at whic the supplemental piston .and the main piston make strokes are equal, means for supplying ex losive mixture to said supplemental cylin er, the ends of said two cylinders bein interconnected by a passage of which the en is never covered by the main piston in its movement, and a chamber in which air is- 'a main cylinder and piston, a supplemental cylinder and piston, means interconnecting said two pistons whereby the rates at which the supplemental piston and the main piston make strokes are equal, means for supplyin ex losive mixture to said supplemental cy loo in er, the ends of said two cylinders being .interconnected by a passage, and a chamber in which airis compresed by the main piston on its explosion stroke said main cylinder being provided with ex aust ports and with air-inlet ports which are uncovered at the end of the explosion Cstroke of the main piston, said air-inlet ports communicating with said chamber,- said exhaust ports being closed early in the return-stroke of the main piston to trap in the main cylinder the-air supplied through the air-inlet ports. i'

24. A two-stroke cycle engine, comprising a.` main cylinder and piston, a supplemental cylinder and piston, means interconnecting said two pistons whereby the rates at which the supplemental piston and the main piston explosive mixture to said supplemental cy inder, the ends ,of said two cylinders being interconnected by a passage of which the end by the main piston in its movement, and a chamber in which air is make strokes are equal, means for supplyinlg 1 25 municating with said chamber.

25. A two-stroke cyclevengine, comprisin a main cylinder andpist-on, a supplementa cylinder and piston, means interconnecting said two pistons whereby the rates at which the supplemental piston and the main piston make strokes are equal, means for supplying explosive mixture to said supplemental cylinder, the ends of said two cylinders being in'- terconnected by a passage, and a chamber inl which air is compressed by strokesofboth pistons, said main cylinder bein provided with exhaust ports and with air-inlet ports which are uncovered at the end ofthe exlosion stroke of the main piston, said airinlet ports communicating with said chamber, said exhaust ports being closed early in ythe return-stroke of the main piston to trap inthe main cylinder the air supplied through thew air-inlet ports.

' 26.' A two-stroke cycle engine, comprising amain cylinder and piston, a supplemental cylinder and piston, means interconnecting said two pistons whereby the rates at which the supplemental piston and the main piston make strokes are equal, means for. supplying explosive mixture to said supplemental cylinder, thelends of said two cylinders being interconnected by a passage of Which the end is never covered by the main 'piston in its movement, a chamber in which air is compressed by the main piston on its. explosion stroke, said main cylinder` being provided with exhaust ports and with air-inlet ports which are uncovered at the end ofthe explosion stroke ofthe main piston, said air'- inlet ports communicating with said chamber, and a spark plugl having its electrodes locatedvin sa1d passage.

2l. A two-stroke cycle internal-combustion engine, comprising a main cylinder and piston, a supplemental cylinder and'piston,said two pistons being arranged to operate with equal rates of strokes, said main cylinder being provided with exhaust and air-inlet -ports which are'intermittently opened and plosive mixture-is drawn into the supple. mental cylinder, a passage leading from the end of saidl supplemental cylinder and conv tinuously opening into the com ression space of the maincylinder, and a va vein the passage -from the supplemental cylinder to the compression space of the main cylinder for preventing back-flow from the main cylinder -to the supplemental cylinder.

28. A two-stroke cycle internal-combustion engine, comprising a main cylinder and piston, a supplemental cylinder and piston, said two pistonsl being. arranged .to yoperatev with equal rates of strokes, said main cylinder .being provided with exhaust and air-intake ports which are intermittently opened and closed during the engine operation; acarbureting device through which explosive mixture is drawn into the supplemental cylinder, a passage leading from theend' of said supplemental cylinder and continuously opening into the compression space ofthe main cylinder, and a valve in thepassage from the supplemental cylinder to the compression space of the main cylinder for preventing back-flow from the main cylinder to thesupplemental cylinder.

' 29. A two-stroke cycle internal-combus-- tion engine,- comprising a main cylinder and piston, a supplementa cylinder and piston,

said two pistons being arranged to operate with equal rates of strokes, said main cylinder being-provided with exhaust and` air- .intake ports which are intermittently opened and closed during the engine operatlon, a carbureting device through which explosive mixture is drawn into the supplemental cylinder, 'a passage leading from said supplemental cylinder and continuously opening vinto the vcompression space of the mam cylinder, a valve-in the passage from the supplemental cylinder -to the ,compression space of the main cylinder for preventing backlow from the main cylinder to the supplemental cylinder2 said valve being located in said passage with a space between it and .said combustion space of the main. cylinder,

and igniting means associated with said space betweensaid valve and combustion space.

In witness whereof, I have hereunto set `my hand at Indianapolis, Indiana, this l8th day of'- September, A. D. one Ithousand nine hundred and twenty-two.. 

